Comparison of the rate capability of nanostructured amorphous and anatase TiO_2 for lithium insertion using anodic TiO_2 nanotube arrays

摘要

Nanostructured amorphous and anatase Ti02 are both considered as high rate Li-insertion/extraction electrode materials. To clarify which phase is more desirable for lithium ion batteries with both high power and high density, we compare the electrochemical properties of anatase and amorphous TiO_2 by using anodic TiO_2 nanotube arrays (ATNTAs) as electrodes. With the same morphological features, the rate capacity of nanostructured amorphous TiO_2 is higher than that of nanostructured anatase TiO_2 due to the higher Li-diffusion coefficient of amorphous TiO_2 as proved by the electrochemical impedance spectra of an amorphous and an anatase ATNTA electrode. The electrochemical impedance spectra also prove that the electronic conductivity of amorphous TiO_2 is lower than that of anatase Ti02. These results are helpful in the structural and componential design of all TiO_2 mesoporous structures as anode material in lithium ion batteries. Moreover, all the advantages of the amorphous ATNTA electrode including high rate capacity, desirable cycling performance and the simplicity of its fabrication process indicate that amorphous ATNTA is potentially useful as the anode for lithium ion batteries with both high power and high energy density.